As integrated circuit devices become more highly integrated, the distances between circuits formed on a semiconductor wafer are reduced. Accordingly, patterned layers formed on the semiconductor substrate have reduced spaces therebetween. When implanting such patterned layers, charge may accumulate on the structures of the patterned layer. This "charge-up" phenomenon may result in electric fields which damage the structures of these finely patterned layers. Anisotropic etching processes may also result in damaging charge accumulation. In particular, the thin insulating films used in polysilicon thin film transistor LCD processes can be readily damaged as a result of the "charge-up" phenomenon.
When ions are implanted into a wafer, the implanted ions collide with atoms of the wafer generating secondary electrons which are emitted from the wafer. The number of secondary electrons emitted varies according to the composition and the physical configuration of the wafer. In general, a larger number of secondary electrons are emitted from a conductor than from an insulator, and the number of secondary electrons emitted increases as the area of the structure increases. Referring to FIG. 1, for example, the number of secondary electrons emitted from the patterned polysilicon layers A and B is approximately two to four times greater than the number of secondary electrons emitted from the patterned oxide layer C.
While each of the patterned polysilicon layers A and B and the patterned oxide layer C are positively charged, the charge of polysilicon layer B is greater than that of polysilicon layer A because of the difference in the surface areas of the layers. Accordingly, a potential difference is generated between polysilicon layers A and B. The electric field resulting from this potential difference may be relatively strong when the two charged polysilicon layers are closely spaced.
The oxide layers C and the active region D between the charged polysilicon layers A and B may thus be affected by the electric field. If the electric field is strong enough, electrons from the oxide pattern C and the active region D may migrate to the polysilicon layers A and B. Furthermore, electrons from the active region D may be more easily subjected to migration than electrons from a nonconductive substrate E such as a quartz substrate. This migration of electrons may result in a deterioration of the oxide layer C and may even lead to the formation of a short circuit between the polysilicon layers A and B and the active region D.
In order to reduce damage resulting from this "charge-up" phenomenon, there have been proposed methods for showering the semiconductor structure with electrons after performing the ion implantation. Although this process can neutralize the charge of the structure, thus reducing the effects of charge-up, damage may still occur.
The layout of a semiconductor device which has been damaged as a result of the "charge-up" phenomenon is illustrated in FIG. 2. A long conductive pattern 14 and a short conductive pattern 10 are arranged adjacent to an active region 12. When ions are implanted into a substrate having such a structure, secondary electron emission may occur, and the long and short conductive patterns 14 and 10 may become positively charged. Because the charge on the longer conductive pattern 14 (with a larger surface area) is greater than that of the shorter conductive pattern 10 (with a smaller surface area), a potential difference is generated between the conductive patterns 10 and 14. The electric field resulting from this potential difference is strongest where the conductive patterns are most closely spaced.
An insulating film may be located between the active region 12 and the conductive patterns 10 and 14. Portions of the active region 12 and the insulating film are thus located within the strongest portions of the electric field between the conductive patterns 10 and 14. The insulating film may be relatively thin, and more particularly, may be thinner than the space between the conductive patterns 10 and 14. Electrons from the insulating film and the active region 12 may thus migrate to the conductive patterns 10 and 14 under the influence of the electric field.
The electric field may be directed from the longer pattern 14 toward the shorter pattern 10 with the electrons migrating toward the longer conductive pattern 14. If the distance between the conductive patterns 10 and 14 is relatively short, an electric field with sufficient strength to damage the insulating film may be generated. Accordingly, the conductive patterns 10 and 14 may be connected to the active region 12 through damaged portions of the insulating film. Because the active region 12 is conductive, the conductive patterns 10 and 14 are thus shorted. Even if not shorted, the migration of electrons from the active area to the conductive patterns may result in a decreased conductivity of the active region.
As discussed above, the insulating film of a conventional semiconductor device may be damaged due to the "charge-up phenomenon". The resulting short circuits may reduce the yield of the semiconductor devices thus produced.